It’s sounds so simple--it’s a biological imperative--but many people have to consciously remind themselves to breath properly when they are anxious.  Anxiety can cause people to exhale incompletely, breath to fast, or forget to breath.  Breathing is essential when you are speaking because it powers the voice and relaxes the body.  Below are some tips on proper breathing that should help you breath normally when you present.

• Your voice rests on your breath.  Inhale before you begin to speak and support your words with your breath as you exhale.  (When you are at rest, you inhale and exhale for roughly the same amount of time.  When you speak you inhale quickly and exhale slowly).  
• Inhale between sentences and phrases and don’t wait until you are completely out of breath to inhale
• Your breathing may slow or increase due to nervousness.  These changes can physiologically exacerbate feelings of anxiety.  If you notice that you are nervous, dizzy or your thinking is cloudy, take several deep breaths.  Make sure that you continue to breath at an appropriate rate
• Develop awareness of tension in your throat chest and stomach.  Tension interferes with your breath and your voice
• Increase the volume of your voice by increasing the amount of breath that supports your voice